JPH0514000B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for forming a transparent phosphor film and a method for manufacturing a transparent phosphor. More specifically, the present invention relates to a method of forming a transparent phosphor film by gelling a sol of phosphor constituents, and a method of producing a transparent phosphor.

In most cases, phosphors are used in the form of a fluorescent film made up of fine particles with a size of several microns to several tens of microns. Since the fluorescent film is made up of fine particles of this size, the following problems may occur. Even when fluorescent light is emitted from a certain phosphor particle, the light hits other phosphor particles several times before exiting the phosphor surface, and is irregularly reflected on the surface. After that, it exits the fluorescent surface. In the case of the fluorescent surface of a cathode ray tube, the influence of this irregular reflection is strong because the fluorescent light emitted from the inner surface is viewed from the outside. As a result, "fogging" occurs in the image, which deteriorates the contrast and causes a decrease in brightness.

Therefore, if it is possible to create a fluorescent film or a similar fluorescent film that is not composed of fine particles and has no voids between particles, the brightness will be improved, and the contrast and sharpness will also be significantly improved.

In the present invention, the highly translucent phosphor film is a phosphor film with extremely few voids in the phosphor film, and is transparent or has so-called high translucency with extremely little diffused reflection (plate-shaped fluorescein film). (including the body).

Conventionally, the following methods have been used to achieve the same object as the present invention.

One method is vacuum deposition. In this method, ordinary phosphor powder is placed in a vapor source and vapor-deposited onto a plate under a vacuum of 5×10 ^-5 mmHg or higher. Here, if the vapor deposition is stopped midway, the raw material phosphor and the resulting phosphor film will have different compositions, so it is necessary to vapor-deposit them all. In addition, the components of the raw material that are easy to fly fly away first, and even if all of the raw material is vapor-deposited, a phosphor surface with a considerably different composition is likely to be formed depending on the phosphor.

The highly translucent fluorescent film thus produced exhibits almost no fluorescence as it is. This is because the activator does not completely enter the matrix of the phosphor.
This is said to be due to the fact that most of the parent material is in an amorphous state and not in a crystalline state. Therefore, if this vapor-deposited film is appropriately heated, the matrix crystallizes and the activator diffuses into the matrix, resulting in light emission.

The phosphor for which this method is most suitable is a self-activating phosphor. The heat treatment must be carried out under very strict conditions regarding time and temperature, which is actually quite difficult. The method devised for this purpose is to heat the plate to be deposited in advance and perform the deposition. According to this method, the deposition time can be shortened and the processing temperature can be lowered.

Another method for producing a highly transparent fluorescent film is a gas phase reaction method (chemical paper deposition). In this method, a phosphor produced by a gas phase reaction is attached to a substrate. This method can be used with zinc sulfide based phosphors. Specifically, hydrogen sulfide is injected into a container connected to a vacuum system at a pressure of 1 to 2 mmHg. The substrate held inside the container is preheated to 500 to 600°C. A small amount of a mixture of metallic zinc and manganese chloride is dropped into this container. This reacts with hydrogen sulfide, resulting in ZnS:
Mn adheres to the substrate. However, the phosphors that can be manufactured using this method are limited.

The present invention is fundamentally different from the above-mentioned vapor deposition method and gas phase reaction method, and uses a sol-gel method to produce a highly transparent fluorescent film. This method provides a highly transparent fluorescent film that is much cheaper than conventional methods, and its industrial advantages are immeasurable.

In addition, the sol-gel method referred to in the invention is a method in which a sol is formed by hydrolyzing an organic acid metal compound or metal salt such as a metal alkoxide or metal acetate of the target fluorescent compound as a starting material, and this sol is turned into a gel. This is the way to do it.

The sol-gel method will be explained below using as an example a composite metal salt phosphor (hereinafter referred to as a lanthanide aluminate phosphor) in which the starting material is a metal alkoxide and the phosphor is a lanthanoid metal and aluminum. The present invention will be explained. Lanthanide-based aluminate phosphors have conventionally been made from a matrix of lanthanide-based metal oxides and aluminum oxide.
Thoroughly mix the lanthanoid metal oxide that will serve as the activator, add a flux if necessary, and heat to 1500℃.
It was obtained by firing at high temperatures ranging from 2,000°C to even higher for over 10 hours. However, according to such conventional methods, the obtained lanthanide-based aluminate phosphor is a powder or a phosphor with an irregular shape. Therefore, in order to obtain the desired highly transparent fluorescent film, a method such as vapor deposition must be used. In addition, in the conventional method, the firing temperature is high and firing is required for a long time, so it cannot be easily manufactured, which has been a big problem in industry. Furthermore, in the conventional method, when the powder is obtained, the particle size distribution of the powder is non-uniform. In order to obtain particles with a constant particle size, it is necessary to further perform classification, etc., resulting in a significantly low yield. Furthermore, the desired particle size cannot always be obtained.

In order to solve the problems of the prior art as described above, the present inventors have conducted various studies in order to obtain a lanthanide aluminate fluorescent film that can be used at a lower temperature, exhibits high translucency, and has a desired shape and particle size. As a result, when gelling the sol obtained by hydrolyzing the alkoxide of the metal component constituting the desired lanthanide-based aluminate phosphor, the subsequent firing is performed at a low temperature and in a short time. It has been found that this process can be carried out easily and that a highly transparent lanthanoid aluminate phosphor having a desired shape and particle size and exhibiting high light transmittance can be obtained.

That is, the method for producing a lanthanoid aluminate phosphor of the present invention includes (i) a lanthanide sol (two types, a matrix and an activator) obtained by hydrolyzing a lanthanide metal alkoxide; Mixture with aluminum sol obtained by hydrolyzing aluminum alkoxide (ii) By hydrolyzing a mixture of lanthanoid metal alkoxide (two types of base and activator) and aluminum alkoxide After gelling at least one of the sol thus obtained and (iii) the composite lanthanide aluminum sol obtained by hydrolyzing the alkoxide of the composite of lanthanoid metal and aluminum, ℃
It is characterized by being fired at a temperature of 1300°C to 1300°C.

In addition, the lanthanoid referred to in the present invention has an atomic number of 57.
from lanthanum to lutetium with atomic number 71.15
rare earth elements La, Ce, Pr, Nd, Pm, Sm,
It is a general term for Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Y with atomic number 39.

The above sol mixture (i) can be obtained, for example, as follows.

After reacting an anhydrous halogenated lanthanide and an alkali metal alkoxide in alcohol, the solvent is replaced with benzene, and the alkali metal halide produced is removed by precipitation to obtain a benzene solution of the lanthanide alkoxide. Next, water is added to this solution and hydrolyzed to obtain a lanthanide sol, which is a sol of lanthanide hydroxide. On the other hand, for example, 100 mol of water is added to 1 mol of aluminum alkoxide and hydrolyzed at 75°C, and then 0.1 mol of hydrochloric acid is added to 1 mol of the aluminum alkoxide and peptized at 95°C. Get Sol. A sol mixture (i) is obtained by mixing the lanthanide sol and the aluminum sol.

The above sol (ii) can be obtained, for example, as follows.

The lanthanoid alkoxide and aluminum alkoxide are dissolved in benzene with the quantity ratio adjusted so that the desired composition ratio of the lanthanide aluminate phosphor is obtained. Next, after refluxing this solution for 4 hours, water is added and hydrolyzed to obtain sol (ii).

The above composite sol (iii) can be obtained, for example, as follows.

Synthesize an alkali metal alcoholate by reacting an alkali metal with excess alcohol in a nitrogen stream,
Aluminum alkoxide in an equimolar amount to the alkali metal is added thereto, and the mixture is refluxed for about 2 hours to synthesize alkali metal aluminum alkoxide. This was added to a lanthanoid halide alcohol solution, and after refluxing and reacting for 4 hours, the solvent was replaced with benzene,
The generated alkali metal halide is precipitated and removed by filtration to obtain a benzene solution of lanthanide aluminum alkoxide. Next, water is added to this solution and hydrolyzed to obtain a composite lanthanide aluminum sol (iii). In this case, a small amount of lanthanide alkoxide or aluminum alkoxide may be added to the lanthanide aluminum alkoxide before hydrolysis to facilitate the formation of a lanthanide aluminate phosphor of the desired composition.

The halogen of the halide used in the above sol preparation may be any of fluorine, chlorine, bromine and iodine, but chlorine is particularly suitable from the viewpoint of reaction stability. The alcohol used is monohydric alcohol such as methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, butyl alcohol, isobutyl alcohol, s-butyl alcohol, amyl alcohol, and isoamyl alcohol, but isopropyl alcohol is especially It is preferable since it does not cause problems such as coloring.

In the method of the present invention, gelation of the sol in (i), (ii) and/or (iii) above is carried out by removing water or the like. In order to form a transparent thin film or thick film through this gelation, the above-mentioned sol is preferably placed in a container with low surface energy such as polystyrene, polypropylene, or Teflon and dried. A method of coating on a quartz substrate or the like is also good.

In addition, to obtain a spherical powder through gelation, the sol is stirred in a non-aqueous solvent containing a surfactant to form a spherical sol using the difference in interfacial tension between the sol and the solvent, and then water is added. is removed and gelled.
By adjusting the stirring speed at this time, a spherical gel material having a diameter of about several μm to about 1 mm can be obtained. In the method of the present invention, by baking the gel material formed as follows for a short time at a temperature of 300°C to 1300°C, a highly translucent phosphor composed of the desired lanthanoid aluminate phosphor is produced. A membrane is obtained. The luminescence spectrum of the obtained fluorescent film was exactly the same as that obtained by the conventional method.

According to the method of the present invention as described above, a latanoid aluminate phosphor can be obtained by firing at a lower temperature and in a shorter time than in the conventional method, and the amount of energy consumed is low. Furthermore, according to the method of the present invention,
When trying to obtain a molded product, the desired shape can be obtained immediately, and when trying to obtain a granular product, the particle size can be easily controlled, so it has the great advantage of being able to obtain the desired particle size. be.

Furthermore, the biggest advantage is that a higher brightness ratio can be measured compared to conventional powder products. This is an improvement of 10 to 20% compared to conventional products.

The above explanation was made using a metal alkoxide as the starting material, but in addition to this method, a method using hydrolysis of an organometallic acid, which is a reaction product of an organic acid and a metal halide, or a method using a hydrolysis of a metal halide can be used as well. It can be a membrane.

Examples of the phosphors that can be produced according to the present invention include phosphors for color TVs as indicated by the P number, phosphors for monochrome TVs, phosphors for various electron tubes, phosphors for low-speed electron tubes, There are phosphors for electroluminescence, photoconductors, phosphors for lamps, phosphors for infrared applications, phosphors for phosphorescence, phosphors for radiation, etc., but other known phosphors can also be used. It is.

In particular, oxide phosphors are easy to produce.

The transparency of the phosphor obtained in the present invention was measured as transmittance.

To measure transmittance, use a 30m/m square with a thickness of 1m/m.
A 100 μm thick lanthanide aluminate phosphor with an average particle size of 6 μm was deposited on quartz glass using a conventional method.
coated with a precipitation coating. The transparent phosphor of the present invention is prepared by coating the above-mentioned quartz glass with lanthanoid aluminate sol and drying it naturally.
A smooth gel body of m was obtained. This was fired at 1000°C for 1 hour to obtain an aluminate phosphor.

The measurement sample obtained here was placed on an optical bench in a water drop, and light was irradiated from a tungsten lamp light source at a distance of 100 m/m. After passing through the measurement sample, a photomultiplier was placed at a distance of 10 m/m from the sample. The light was received and the transmittance was measured through 1 m/m thick quartz glass that was not coated with a phosphor. As a result, the transmittance of the phosphor film made by the conventional method was in the range of 5-10%, but the transmittance of the highly transparent phosphor film according to the present invention was in the range of 30-90%.

The present invention can be applied to any field where fluorescent light has been conventionally used without any problem. Furthermore, application to high-definition tubes can be considered. This is the case with penetration type cathode ray tubes.
Currently, particulate phosphor is coated inside the cathode ray tube. The highly transparent fluorescent film of the present invention is applied as follows. Three layers of each of the three colors B, G, and R are coated, and a highly transparent insulator (for example, highly transparent Al ₂ O ₃ , SiO ₂ obtained by the sol-gel method) is coated between the three layers.
membrane). In this way, a penetration type cathode ray tube with higher brightness and better resolution than ever before can be obtained.

This will be explained below using examples.

Example 1 High purity yttrium oxide and ammonium chloride were mixed and reacted at a temperature of 350°C for 1 hour.
The reaction product, anhydrous yttrium chloride, was extracted with ethanol, and the ethanol solvent was replaced with isopropyl alcohol. In addition, an alcoholate obtained by adding metallic sodium to a mixed solution of isopropyl alcohol and benzene and refluxing at 82°C was mixed with the above anhydrous yttrium chloride solution, and after further refluxing at 82°C, the solvent was replaced with benzene. ,
Sodium chloride was removed by filtration to obtain a benzene solution of yttrium isopropoxide. Water was added to this solution for hydrolysis to obtain yttrium sol.

Next, 100 mol of water was added to 1 mol of aluminum alkoxide, hydrolyzed at 75°C, and
Aluminum sol was obtained by adding 0.1 mol of hydrochloric acid and peptizing at 95°C.

The yttrium sol and aluminum sol obtained above were mixed at a molar ratio of (a) 1:1, (b) 3:5, and (c) 1:2, and further cerium sol was added at a ratio of 2.5x to 1 mole of the mixture. 10 ^-3 moles were mixed, placed in a Teflon container, and dried at room temperature to obtain a transparent gel-like molded film. Next, this was fired at 1000°C for 2 hours to produce (a) YAlO ₃ :Ce+Y ₃ Al ₅ O ₁₂ : Ce(b)Y ₃ Al ₅ O ₁₂ :
A highly transparent phosphor film consisting of Ce and (c) Y ₂ Al ₄ O ₉ :Ce was obtained as a cerium yttrium aluminate phosphor. This was identified by X-ray diffraction.

Example 2 Yttrium isopropoxide, aluminum isopropoxide, and cerium isopropoxide were mixed in a benzene solution at a molar ratio of 3:5:5×10 ^-3 and refluxed at a temperature of 82°C for 4 hours. Thereafter, sufficient water was added for hydrolysis to obtain a mixture of yttrium sol, aluminum sol, and cerium sol.

When this was gelled and fired in the same manner as in Example 1, a highly transparent phosphor film consisting of a cerium-activated yttrium aluminate phosphor having the composition formula Y ₃ Al ₅ O ₁₂ :Ce was obtained. . This was identified by X-ray diffraction.

Example 3 Potassium metal was reacted with excess isopropyl alcohol in a nitrogen stream to synthesize potassium isopropoxide [i-C ₃ H ₇ OK], and to this was added aluminum isopropoxide in an equimolar amount to the metal potassium. The mixture was refluxed for a period of time to synthesize potassium aluminum isopropoxide {KAl(i-OC ₃ H ₇ ) ₄ }.
This was added to yttrium chloride isopropyl alcohol solution and cerium chloride isopropyl alcohol solution and refluxed for 4 hours to form yttrium cerium aluminum isopropoxide {Y・Ce[Al
(i-OC ₃ H ₇ ) ₄ ] ₃ } was synthesized. reaction by-products
KCl was separated after replacing the solvent with benzene. Excess distilled water was added to the obtained alkoxide and refluxed to obtain a composite yttrium aluminum cerium sol.

This was molded by gelation in the same manner as in Example 1, and the composition formula was determined by baking at 1000℃.
A highly transparent phosphor film consisting of a cerium-activated yttrium aluminate phosphor of Y ₃ Al ₅ O ₁₂ :Ce was obtained. This was identified by X-ray diffraction.

Example 4 A gadolinium sol was obtained in the same manner as in Example 1 except that high-purity gadolinium oxide was used instead of high-purity yttrium oxide as a starting material.

This gadolinium sol, aluminum sol, and cerium sol were mixed in a molar ratio of 3:5:5×10 ^-3 , formed by gelation, and further baked.
A highly translucent phosphor consisting of a cerium-activated gadolinium aluminate phosphor having a composition ratio of Gd ₃ Al ₅ O ₁₂ :Ce was obtained. This was identified by X-ray diffraction.

Example 5 04 mol per 1 mol of yttrium aluminum cerium isopropoxide {Y.Ce[Al(i-O(C ₃ H ₇ ) ₄ ] ₃ ) obtained by a method similar to that in Example 3 was added. Aluminum isopropoxide [Al(i-O(C ₃ H ₇ ) ₃ )] was added thereto and thoroughly mixed by refluxing for 4 hours, followed by hydrolysis to obtain a sol.

After gelatinizing this sol and baking it at 1000°C for 2 hours, a highly transparent phosphor film consisting of a cerium-activated yttrium aluminate phosphor with a compositional formula of Y ₃ Al ₅ O ₁₂ :Ce was obtained. Ta. This was identified by X-ray diffraction.

Example 6 0.2 mol per 1 mol of yttrium aluminum cerium isopropoxide {Y.Ce[Al(i-O(C ₃ H ₇ ) ₄ ] ₃ ) obtained by a method similar to that in Example 3 was added. Yttrium propoxide [Y(i
-O(C ₃ H ₇ ) ₃ ] and refluxed for 18 hours to thoroughly mix the mixture, followed by hydrolysis to obtain a sol.

When this sol is gelatinized and then baked at 1000°C for 2 hours, a highly transparent phosphor film consisting of a cerium-activated yttrium aluminate phosphor with a compositional formula of YAlO ₃ :Ce (hexagonal) is obtained. Ta. Also, use the above gel
When fired at 1200℃ for 2 hours, the composition formula becomes YAlO ₃ :Ce
A highly transparent phosphor film consisting of a cerium-activated yttrium aluminate phosphor of (orthorhombic, perovskite type) was obtained. These things were identified by X-ray diffraction. .

Example 7 Europium sol was obtained in the same manner as in Example 1. This europium sol was mixed with the yttrium sol obtained in Example 1 at a molar ratio of 1:5 x 10 ^-3 , gelled, and then baked at 1100°C for 2 hours, resulting in a compositional formula of Y ₂ O ₃ :Eu. A highly transparent phosphor film consisting of a phosphor that emits red light was obtained.

Example 8 Silica gel, terbium sol, and europium sol were obtained in the same manner as in Example 1. The various sols obtained above and the yttrium sol obtained in Example 1,
Cerium sol was mixed according to the following formula. _Y2SiO5 : Eu, _Y2SiO5 : _{Tb , Y2SiO5} : _Ce
(However, Eu, Tb, and Ce were 5 x 10 ^-5 moles.) After gelling these sols, they were fired at 1200°C for 2 hours to obtain a phosphor represented by the above formula. This showed red, green, and blue, respectively.

Example 9 The yttrium sol in Example 7 was gelled to obtain 8 μm spherical yttrium oxide. This surface was coated with europium sol, terpium sol, and cerium sol to a thickness of 0.5 μm, and after gelation, it was fired at 1000°C. Europium by firing,
Terpium and cerium diffused into yttrium and became highly translucent phosphor particles. This was identified by X-ray diffraction.

Claims (1)

[Claims] 1. Hydrolyzing a metal alkoxide, an organic acid metal compound, or a metal salt containing each element of the host constituent elements of the phosphor and/or each element of the activator constituent elements of the phosphor. A method for producing a highly translucent phosphor, which is characterized in that a sol is obtained by this process, the sol is then gelled, the obtained sol is used as a raw material for a phosphor, and the phosphor is produced through firing. 2. The method for producing a highly translucent phosphor according to claim 1, wherein the firing temperature is in the range of 500°C to 1300°C. 3. The method for forming a highly translucent phosphor according to claim 2, wherein the gel is spherical. 4. The method for forming a highly translucent phosphor according to claim 3, wherein the diameter of the spherical sol is in the range of several μm to 1 mm.